The invention relates to a filter packing containing electrostatically formed porous microfibers.
A related filter packing is described in German patent DE-OS No. 20 32 072. The fibers employed in this packing often are ribbon-shaped, and they exhibit an irregular, highly porous surface structure. The cross sectional area of the individual pores is enlarged in the vicinity of the surface openings of the pores and their number increases considerably toward the outside surfaces of the fibers. Such fibers have a low mechanical strength and it has been found that the degree of separation of particles obtained with a filter packing formed therefrom seldom achieves desirable levels. For example such filters do not meet the requirements set for typical applications such as air conditioning equipment for nuclear installations, wherein the filters must ensure a high degree of separation of radioactively contaminated particles from air. Another application with similarly stringent requirements is purification of breathing air for which the removal of noxious substances while incurring the lowest possible air resistance is important. Such noxious substances may be contained in solid or liquid suspended particles which are chemically or biologically contaminated.
Therefore, it is an object of the invention to develop a filter packing for use in very fine filtration which allows a high degree of particle separation of such very fine substances while providing low air flow resistance.